Earth boring drill bits with using opposed kerfing for cutters

ABSTRACT

A drill bit configured having eight blades thereon with secondary cutters on four blades using opposed kerfing for the secondary cutters located on four of the blades.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/084,811, filed Jul. 30, 2008, the disclosure of which is incorporated herein in its entirety.

TECHNICAL FIELD

The present invention relates generally to drilling a subterranean borehole and, more specifically, to drill bits using opposed kerfing profiles for cutters.

BACKGROUND OF THE INVENTION

State of the Art: The drilling of wells for any reason, such as oil and gas production, geothermal production, water production, etc. conventionally may employ drill bits using diamond cutters located on a variable number of blades of the drill bit. Typically, drill bits having a fewer number of blades on the drill bit tend to cut faster and have bigger junk slots for the removal of cutting from the well bore than drill bits having more blades. However, when the number of blades on the drill bit and the number of cutters on the drill bit are increased, the loading on each cutter can be reduced, thereby improving cutter life and drill bit life during drilling a well bore.

It would be desirable to reduce the number of blades on a drill bit to increase the rate of penetration of the drill bit in comparison to that of a drill bit having more blades thereon, while reducing individual cutter loading to increase cutter life and drill bit life.

BRIEF SUMMARY OF THE INVENTION

A drill bit configured having multiple blades thereon with secondary cutters on a reduced number of blades (secondary blades) of the drill bit, using opposed kerfing for the secondary cutters located on the secondary blades.

The features and advantages of the present invention will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:

FIG. 1 shows a perspective view of a drill bit;

FIG. 2A shows an enlarged perspective view of an embodiment of the drill bit described herein;

FIG. 2B shows an enlarged perspective view of another embodiment of the drill bit described herein;

FIG. 3A shows an enlarged view of a portion of the face of the drill bit of FIG. 2;

FIG. 3B shows an enlarged view of a portion of the face of the drill bit of FIG. 2;

FIG. 4A shows a schematic side cross-sectional view of a cutting element placement design of a drill bit described herein showing relative exposures of first and second types of cutting elements disposed thereon;

FIG. 4B shows a schematic side cross-sectional view of a cutting element placement design of a drill bit described herein showing alternative relative exposures of first and second types of cutting elements disposed thereon;

FIG. 5A is a perspective view of one configuration of a cutting element for the drill bit;

FIG. 5B is a frontal view of the cutting element;

FIG. 5C is a cross-sectional view taken through line 5C-5C on FIG. 5B;

FIG. 5D is an enlarged view of the cutting edge of the cutting element in the circled area of FIG. 5C; and

FIGS. 6A-6H show schematically other configurations of the cutting elements suitable for a drill bit, wherein FIGS. 6A, 6C, 6E and 6G show transverse configurations of the cutting elements, and FIGS. 6B, 6D, 6F and 6H show side views.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-3 illustrate an embodiment of a drill bit 12 in the form of a fixed cutter or so-called “drag” bit described herein. As shown in FIGS. 1-3, drill bit 12 includes a body 14 having a face 26 and generally radially extending blades 22, forming fluid courses 24 therebetween extending to junk slots 35 between circumferentially adjacent blades 22. Bit body 14 may comprise a tungsten carbide matrix or a steel body, both as well known in the art. Blades 22 may also include pockets 30, which may be configured to receive cutting elements of one type such as, for instance, superabrasive cutting elements in the form of PDC cutting elements 32. Generally, such a PDC cutting element may comprise a superabrasive region that is bonded to a substrate. Rotary drag bits employing PDC cutting elements have been employed for several decades. PDC cutting elements are typically comprised of a disc-shaped diamond “table” formed on and bonded under a high-pressure and high-temperature (HPHT) process to a supporting substrate such as cemented tungsten carbide (WC), although other configurations are known. Drill bits carrying PDC cutting elements, which, for example, may be brazed into pockets in the bit face, pockets in blades extending from the face, or mounted to studs inserted into the bit body, are known in the art. Thus, PDC cutting elements 32 may be affixed upon the blades 22 of drill bit 12 by way of brazing, welding, or as otherwise known in the art. It is also contemplated that cutting elements 32 may comprise suitably mounted and exposed natural diamonds, thermally stable polycrystalline diamond compacts, cubic boron nitride compacts, or diamond grit-impregnated segments, as known in the art and as may be selected in consideration of the subterranean formation or formations to be drilled.

Also, each of blades 22 may include a gage region 25 that is configured to define the outermost radius of the drill bit 12 and, thus the radius of the wall surface of a borehole drilled thereby. Gage regions 25 comprise longitudinally upward (as the casing bit 12 is oriented during use) extensions of blades 22, extending from nose portion 20 and may have wear-resistant inserts or coatings, such as cutting elements in the form of gage trimmers of natural or synthetic diamond, or hardfacing material, on radially outer surfaces thereof as known in the art to inhibit excessive wear thereto.

Drill bit 12 is also provided with pockets 34 in four of the blades 22, which may be configured to receive abrasive cutting elements 36 of similar type as those of the first type of cutting elements 32, cutting elements 36 being located in a second row of cutting elements located behind the cutting elements 32 of the first row on four of the eight blades of the drill bit 12. It is also contemplated that abrasive cutting elements 36 may comprise, for example, a carbide material other than tungsten (W) carbide, such as a Ti, Mo, Nb, V, Hf, Ta, Cr, Zr, Al, and Si carbide, or a ceramic. Abrasive cutting elements 36 may be secured within pockets 34 by welding, brazing or as otherwise known in the art.

As depicted in FIGS. 1-3, abrasive cutting elements 36 may be of substantially uniform or varying thickness, taken in the direction of intended bit rotation. As shown in FIGS. 1-3, abrasive cutting elements 32, 36 may be of varying thickness, taken in the direction of bit rotation, wherein abrasive cutting elements 36 at more radially outward locations (and, thus, which traverse relatively greater distance for each rotation of drill bit 12 than those, for example, within the cone of dill bit 12) may be thicker to ensure adequate material thereof will remain for cutting.

Also as shown in FIGS. 1-3, cutting elements 36 may be placed in an area from the cone of the bit on four blades 22 thereof out to the shoulder (in the area from the centerline L to gage regions 25) to provide cutting elements in similar positions as cutting elements 32, only opposed a desired variable number of degrees rotation, typically 180° rotation, from a corresponding cutting element 32, which additionally allows the cutters 36 in the second row on a blade 22 to sit between adjacent cutters 32 in the row in front of the cutting elements 36 on the blade 22. That is, cutting elements 36′ have substantially the same radial position on the drill bit 12 as the radial positions of cutting elements 36″ only being positioned on blades 22 any desired variable number of degrees of rotation; i.e., substantially 180° from each other on the drill bit 12. Broadly, cutting elements 32 on face 26, which may be defined as surfaces at less than 90°, profile angles, or angles with respect to centerline L. Cutting elements 36 are also placed selectively along the profile of the face 26 to provide enhanced cutting of the drill bit 12 and enhanced durability of the drill bit 12.

Superabrasive cutting elements 32 and superabrasive cutting elements 36 are respectively dimensioned and configured, in combination with the respective depths and locations of pockets 30 and 34, to provide cutting elements 36 with the same relative exposure as cutting elements 32, although cutting elements 36 may have a greater or lesser relative exposure than superabrasive cutting elements 32, if desired. As used herein, the term “exposure” of a cutting element generally indicates its distance of protrusion above a portion of a drill bit, for example, a blade surface or the profile thereof, to which it is mounted. However, in reference specifically to the present invention, “relative exposure” is used to denote a difference in exposure between a cutting element 32 of the one type and a cutting element 36 of the same type. More specifically, the term “relative exposure” may also be used to denote a difference in exposure between one cutting element 32 and another cutting element 36, which are proximately located on drill bit 12 at similar radial positions relative to a centerline L (see FIGS. 4A, 4B) of drill bit 12 but offset from each other by 180° on different blades 22 in a direction of bit rotation.

In the embodiment depicted in FIGS. 1, 2, and 3, cutting elements 36 may generally be described as rotationally “following” some of the cutting elements 32 and in close rotational proximity to on the blades 22 on four of the eight blades of the drill bit 12, as well as being located at substantially the same radius although being offset 180° therefrom another cutting element 32 on an exposed blade 22 of the four blades 22 of the eight blades 22 of the drill bit 12. However, if desired, abrasive cutting elements 36 may also be located to rotationally “lead” associated superabrasive cutting elements 32.

Referring to FIGS. 2A and 3A, in another embodiment of the drill bit 12, cutting elements 36 may be placed in an area from the cone of the bit on four blades 22 thereof out to the shoulder (in the area from the centerline L to gage regions 25) to provide cutting elements in similar positions as cutting elements 32, only opposed 180° from a corresponding cutting element 32, which additionally allows the cutters 36 in the second row on a blade 22 to sit behind adjacent cutting elements 32 in the row in front of the cutting elements 36 on the blade 22. That is, cutting elements 36′ have substantially the same radial position on the drill bit 12 as the radial positions of cutting elements 36″ only being positioned on blades 22 substantially 180°, an angular distance along or around the drill bit 12, from each other on the drill bit 12 and behind the cutting elements 32 located in front thereof. Broadly, cutting elements 32 on face 26, which may be defined as surfaces at less than 90°, profile angles, or angles with respect to centerline L. Cutting elements 36 are also placed selectively along the profile of the face 26 to provide enhanced cutting of the drill bit 12 and enhanced durability of the drill bit 12.

By way of illustration of the foregoing, FIG. 4A shows a schematic side view of a cutting element placement design for drill bit 12 showing cutting elements 32, 36 as disposed on a drill bit (not shown) such as drill bit 12 of the present invention in relation to the longitudinal axis or centerline L and drilling profile P thereof for all 124 cutting elements 32, 36 on the drill bit 12, as if all the cutting elements 32, 36 were rotated onto a single blade (not shown). The plurality of cutting elements 32, 36 are sized, configured, and positioned to drill into any desired subterranean formation. The reduction of drill bit 12 to an eight blade configuration provides a drill bit having a greater rate of penetration during drilling than a drill bit having twelve blades with the durability of a drill bit having twelve blades by substantially maintaining the cutting element loading as the same by using the same number of cutting elements on the drill bit with four of eight blades having two rows of cutting elements thereon and by using opposed kerfing regarding the second row of cutting elements and being located at the same radial position only located 180° angularly as described herein from the same cutting element.

By way of illustration of the foregoing, FIG. 4B shows a schematic side view of a cutting element placement design for drill bit 12 showing cutting elements 32, 36 as disposed on a drill bit (not shown) such as drill bit 12 of the present invention in relation to the longitudinal axis or centerline L and drilling profile P thereof for all 124 cutting elements 32, 36 on the drill bit 12, as if all the cutting elements 32, 36 were rotated onto a single blade (not shown) when the cutting elements 36 in the second row of cutting elements on the four blades of the eight blades are located directly behind the cutting elements 32 on the four blades having the same exposure as the cutting elements 32. The plurality of cutting elements 32, 36 are sized, configured, and positioned to drill into any desired subterranean formation. In this instance, the reduction of drill bit 12 to an eight blade configuration provides a drill bit having approximately the same rate of penetration during drilling as a drill bit having twelve blades with the durability of a drill bit having twelve blades by substantially maintaining the loading on the cutting elements as the same by using the same number of cutting elements on the drill bit with four of eight blades having two rows of cutting elements thereon and by using opposed kerfing regarding the second row of cutting elements and being located at the same radial position only located 180° from the same cutting element.

FIGS. 5A-5D depict one example of a suitable configuration for cutting elements 36, including a disc-like body 100 of tungsten carbide or other suitable material and having a circumferential chamfer 102 at the rear (taken in the direction of intended cutter movement) thereof, surrounding a flat rear surface 104. A cylindrical side surface 106 extends from chamfer 102 to an annular flat 108 oriented perpendicular to longitudinal axis 110 and extending inwardly to offset chamfer 112, which leads to flat cutting face 114. An area from the junction of side surface 106 with annular flat 108 to the junction of offset chamfer 112 with cutting face may be generally termed the cutting edge area, for the sake of convenience. The angles of chamfer 102 and offset chamfer 112 may be, for example, 45° to longitudinal axis 110. However, other angles are contemplated and a specific angle is not limiting of the present invention. Cutting elements 36 may be disposed on the face 26 (as on blades 22) of drill bit 12 at, for example, a forward rake, a neutral (about 0°) rake or a back rake of up to about 25°, for effective cutting of a casing shoe, casing bit, cementing equipment components, and cement, although a specific range of back rakes for cutting elements 36 is not limiting of the present invention.

FIGS. 6A-6H depict other suitable configurations for cutting elements 36. The cutting element 36 depicted in FIGS. 6A and 6B is circular in transverse configuration and, as shown in FIG. 6B, has a cutting edge area configured similar to that of cutting element 36 depicted in FIGS. 5A-5D. However, rear surface 104 is sloped toward the front of the cutting element (in the intended cutting direction shown by the arrow), providing a thicker base and a thinner outer edge for cutting, to enhance faster wear when formation material is engaged. The cutting element 36 depicted in FIGS. 6C and 6D is also circular in transverse configuration and, as shown in FIG. 6D, has a cutting edge area configured similar to that of cutting element 36 depicted in FIGS. 5A-5D. However, rear surface cutting face 114 is sloped toward the rear of the cutting element, providing a thicker base and a thinner outer edge for cutting, to enhance faster wear when formation material is engaged. The cutting element 36 depicted in FIGS. 6E and 6F is also circular in transverse configuration and, as shown in FIG. 6F, has a cutting edge area configuration similar to that of cutting element 36 depicted in FIGS. 5A-5D. However, cutting face 114 is sloped toward the rear of the cutting element from the cutting edge area, providing a thinner base and a thicker outer edge for cutting, to provide more cutting element material for extended cutting of casing components and the like. The cutting element 36 depicted in FIGS. 6G and 6H is ovoid or egg-shaped in transverse configuration and, as shown in FIG. 6H, has a cutting edge area similar to that of cutting element 36 depicted in FIGS. 5A-5D. Cutting face 114 and rear surface 104 are mutually parallel. The ovoid configuration provides enhanced loading of material being cut by the cutting element to facilitate initial engagement thereby.

Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some exemplary embodiments. Similarly, other embodiments of the invention may be devised that do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims, are to be embraced thereby. 

1. A drill bit for drilling a subterranean formation comprising: a bit body having a face, a plurality of primary blades, and a plurality of secondary blades, each secondary blade of the plurality of secondary blades located between two blades of the plurality of primary blades; a first plurality of cutting elements disposed on a first blade of the plurality of primary blades in radial positions thereon; a second plurality of cutting elements disposed on the first blade of the plurality of primary blades, the second plurality of cutting elements being disposed in radial position behind the first plurality of cutting elements being located in radial position at one of substantially between the cutting elements disposed in front thereof and substantially behind the cutting elements disposed in front thereof; a third plurality of cutting elements disposed in radial positions on a first blade of the plurality of secondary blades, the first blade of the plurality of secondary blades located adjacent the first blade; a fourth plurality of cutting elements disposed on a second primary blade of the plurality of blades; and a fifth plurality of cutting elements disposed on the second blade of the plurality of primary blades in radial positions thereon, the fifth plurality of cutting elements being disposed in radial positions behind the fourth plurality of cutting elements being located substantially between the cutting elements disposed in front thereof, at least some of the fifth plurality of cutting elements having substantially the same radial positions on the drill bit as the radial positions of the first plurality of cutting elements on the first blade of the plurality of primary blades.
 2. The drill bit of claim 1, wherein the drill bit includes one of an even number of blades thereon and an odd number of blades thereon.
 3. The drill bit of claim 2, wherein a plurality of cutting elements of the at least one type and a plurality of cutting elements of at least another, different type are disposed on each blade.
 4. The drill bit of claim 1, wherein the first, second, third, fourth, and fifth cutting elements are disposed in pockets formed in the blades.
 5. The drill bit of claim 1, wherein the first, second, third, fourth, and fifth cutting elements comprise one of superabrasive cutting elements and abrasive cutting elements.
 6. The drill bit of claim 5, wherein the superabrasive cutting elements comprise PDC cutting elements and the abrasive cutting elements comprise tungsten carbide cutting elements.
 7. The drill bit of claim 1, wherein a central portion of an outer profile of the face is configured as an inverted cone and is surrounded by a nose.
 8. The drill bit of claim 1, wherein cutting elements are selected from the group consisting of a PDC cutting element, a thermally stable diamond cutting element, and a natural diamond cutting element.
 9. The drill bit of claim 1, wherein the cutting elements are selected from the group consisting of a tungsten carbide cutting element, another metal carbide cutting element and a ceramic.
 10. The drill bit of claim 1, wherein the second primary blade of the plurality of primary blades is located approximately 180° circumferentially from the first blade of the plurality of primary blades.
 11. A drill bit for drilling a subterranean formation comprising: a bit body having a face at a leading end thereof and a plurality of blades; a first plurality of cutting elements disposed on a first blade of the plurality of blades in radial positions thereon; a second plurality of cutting elements disposed on the first blade of the plurality of blades, the second plurality of cutting elements being disposed in radial position behind the first plurality of cutting elements being located in radial position at one of substantially between the cutting elements disposed in front thereof and substantially behind the cutting elements disposed in front thereof; a third plurality of cutting elements disposed in radial positions on a second blade of the plurality of blades, the second blade located adjacent the first blade; a fourth plurality of cutting elements disposed on a third blade located approximately 180° circumferentially from the first blade of the plurality of blades in radial positions thereon; and a fifth plurality of cutting elements disposed on the third blade of the plurality of blades in radial positions thereon, the fifth plurality of cutting elements being disposed in radial positions behind the fourth plurality of cutting elements being located substantially between the cutting elements disposed in front thereof, at least some of the fifth plurality of cutting elements having substantially the same radial positions on the drill bit as the radial positions of the first plurality of cutting elements on the first blade.
 12. The drill bit of claim 11, wherein the drill bit includes one of an even number of blades thereon and an odd number of blades thereon.
 13. The drill bit of claim 12, wherein a plurality of cutting elements of the at least one type and a plurality of cutting elements of at least another, different type are disposed on each blade.
 14. A drill bit for drilling a subterranean formation comprising: a bit body having an even number of blades; a first plurality of cutting elements disposed on a first blade of the plurality of blades in radial positions thereon; a second plurality of cutting elements disposed on the first blade of the plurality of blades, the second plurality of cutting elements being disposed in radial position behind the first plurality of cutting elements being located in radial position substantially behind the cutting elements disposed in front thereof; a third plurality of cutting elements disposed in radial positions on a second blade of the plurality of blades, the second blade located adjacent the first blade; a fourth plurality of cutting elements disposed on a third blade located approximately 180° circumferentially from the first blade of the plurality of blades in radial positions thereon; and a fifth plurality of cutting elements disposed on the third blade of the plurality of blades in radial positions thereon, the fifth plurality of cutting elements being disposed in radial positions behind the fourth plurality of cutting elements being located substantially behind the cutting elements disposed in front thereof, at least some of the fifth plurality of cutting elements having substantially the same radial positions on the drill bit as the radial positions of the first plurality of cutting elements on the first blade.
 15. The drill bit of claim 14, wherein the first, second, third, fourth, and fifth cutting elements are disposed in pockets formed in the blades.
 16. The drill bit of claim 14, wherein the first, second, third, fourth, and fifth cutting elements comprise one of superabrasive cutting elements and abrasive cutting elements.
 17. A drill bit for drilling a subterranean formation comprising: a bit body having an even number of blades; a first plurality of cutting elements disposed on a first blade of the plurality of blades in radial positions thereon; a second plurality of cutting elements disposed on the first blade of the plurality of blades, the second plurality of cutting elements being disposed in one of a radial position including one of substantially behind the cutting elements disposed in front thereof and substantially behind the cutting elements disposed in front thereof; a third plurality of cutting elements disposed in radial positions on a second blade of the plurality of blades, the second blade located adjacent the first blade; a fourth plurality of cutting elements disposed on a third blade located less than approximately 180° circumferentially from the first blade of the plurality of blades in radial positions thereon; and a fifth plurality of cutting elements disposed on the third blade of the plurality of blades in radial positions thereon, the fifth plurality of cutting elements being disposed in radial positions including one of substantially behind the cutting elements disposed in front thereof and substantially behind the cutting elements disposed in front thereof, at least some of the fifth plurality of cutting elements having substantially the same radial positions on the drill bit as the radial positions of the first plurality of cutting elements on the first blade. 